md: allow resync_start to be set while an array is active.
The sysfs attribute 'resync_start' (known internally as recovery_cp),
records where a resync is up to. A value of 0 means the array is
not known to be in-sync at all. A value of MaxSector means the array
is believed to be fully in-sync.
When the size of member devices of an array (RAID1,RAID4/5/6) is
increased, the array can be increased to match. This process sets
resync_start to the old end-of-device offset so that the new part of
the array gets resynced.
However with RAID1 (and RAID6) a resync is not technically necessary
and may be undesirable. So it would be good if the implied resync
after the array is resized could be avoided.
So: change 'resync_start' so the value can be changed while the array
is active, and as a precaution only allow it to be changed while
resync/recovery is 'frozen'. Changing it once resync has started is
not going to be useful anyway.
This allows the array to be resized without a resync by:
write 'frozen' to 'sync_action'
write new size to 'component_size' (this will set resync_start)
write 'none' to 'resync_start'
write 'idle' to 'sync_action'.
Also slightly improve some tests on recovery_cp when resizing
raid1/raid5. Now that an arbitrary value could be set we should be
more careful in our tests.
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5469ae3..aa640a8 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3324,7 +3324,7 @@
char *e;
unsigned long long n = simple_strtoull(buf, &e, 10);
- if (mddev->pers)
+ if (mddev->pers && !test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
return -EBUSY;
if (cmd_match(buf, "none"))
n = MaxSector;